thanks everyone, all comments were very much appreciated. well, in this case, a lesson learned the hard way then.

I have entered into a mining contract with miners on ebay, we agree this following contracts:
1. 30days 2.7Th/s @$200
2. 30days 7.5Th/s @$300

the later is much cheaper I guess. my mining pool is at antpool. my question is, did I make a good deal or was I fooled? any advice on decent mining contract. all are for btc coin mining on different person.